Ferroelectric polarization tailored spin polarized electronic structure and magnetic anisotropy in two-dimensional ScSi₂N₄/CuInP₂S₆ multiferroic heterostructures

Two-dimensional (2D) van der Waals (vdW) multiferroic heterostructures which consist of vdW intrinsic magnets and ferroelectrics (FEs) plays an extremely important role in novel 2D spintronic devices. In this paper, the electronic structure and magnetic anisotropy of 2D vdW ScSi2N4/CuInP2S6 heterostructure are systematically investigated using first-principles calculation. CuInP2S6 is a 2D FE material with out-of-plane polarization, and ScSi2N4 is a half-metal with ferromagnetic (FM) properties. After the ab initio molecular dynamics simulations, the structures of upward polarization (P up arrow) and downward polarization (P down arrow) states are stable. Both the P up arrow and P down arrow states of ScSi2N4/CuInP2S6 heterostructure are FM half-metals. Biaxial strains modulate the electronic structure and magnetic properties of the ScSi2N4/CuInP2S6 heterostructure. With the application of compressive strains in P down arrow state, the spin-up band crosses Fermi level and the P down arrow state changes from half-metal to metal. The transition from half-metal to metal in P up arrow state is realized at epsilon = -4% and epsilon= -6%. The magnetic anisotropy energy of the P down arrow state can be enhanced by compressive strains of -2% and -4%. The P down arrow state shows the largest average planar electrostatic potential of 0.819 eV at epsilon = -6%, which keeps the maximum electrostatic field between ScSi2N4 and CuInP2S6 monolayers. As the strain increases from -2% to -6%, the potential difference of P up arrow state increases gradually. At +6% tensile strain, the band structure inversion occurred in both P up arrow and P down arrow states. These results demonstrate the potential of 2D vdW multiferroic heterostructures and can enrich the field of spintronic devices.